In REST API, there are two parts, client and server.
For REST API client, 1) will be helpful. Especially, webread for HTTP GET request and webwrite for HTTP POST request.
Also, there is matlab.net.http command which will be used for accessing compilcated REST API endpoint.
For REST API server, MATLAB Production Server has functions for deploying MATLAB codes to REST API. From REST API clients such as HTML/JavaScript, you can call MPS's endpoint.
I suppose your client will provide REST API server, so you might need to call it from MATLAB. So, 1) would be your choice.